1. Field of the Invention
The field of the invention relates to transmissions. More particularly the invention relates to continuously variable transmissions.
2. Description of the Related Art
In order to provide an infinitely variable transmission, various traction roller transmissions in which power is transmitted through traction rollers supported in a housing between torque input and output discs have been developed. In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause the engagement of traction rollers with the torque discs in circles of varying diameters depending on the desired transmission ratio.
However, the success of these traditional solutions has been limited. For example, in U.S. Pat. No. 5,236,403 to Schievelbusch, a driving hub for a vehicle with a variable adjustable transmission ratio is disclosed. Schievelbusch teaches the use of two iris plates, one on each side of the traction rollers, to tilt the axis of rotation of each of the rollers. However, the use of iris plates can be very complicated due to the large number of parts which are required to adjust the iris plates during shifting the transmission. Another difficulty with this transmission is that it has a guide ring which is configured to be predominantly stationary in relation to each of the rollers. Since the guide ring is stationary, shifting the axis of rotation of each of the traction rollers is difficult. Yet another limitation of this design is that it requires the use of two half axles, one on each side of the rollers, to provide a gap in the middle of the two half axles. The gap is necessary because the rollers are shifted with rotating motion instead of sliding linear motion. The use of two axles is not desirable and requires a complex fastening system to prevent the axles from bending when the transmission is accidentally bumped, is as often the case when a transmission is employed in a vehicle. Yet another limitation of this design is that it does not provide for an automatic transmission.
Therefore, there is a need for a continuously variable transmission with a simpler shifting method, a single axle, and a support ring having a substantially uniform outer surface. Additionally, there is a need for an automatic traction roller transmission that is configured to shift automatically. Further, the practical commercialization of traction roller transmissions requires improvements in the reliability, ease of shifting, function and simplicity of the transmission.
The present invention includes a transmission for use in rotationally or linearly powered machines and vehicles. For example the present transmission may be used in machines such as drill presses, turbines, and food processing equipment, and vehicles such as automobiles, motorcycles, and bicycles. The transmission may, for example, be driven by a power transfer mechanism such as a sprocket, gear, pulley or lever, optionally driving a one way clutch attached at one end of the main shaft.
In one embodiment of the invention, the transmission comprises a rotatable driving member, three or more power adjusters, wherein each of the power adjusters respectively rotates about an axis of rotation that is centrally located within each of the power adjusters, a support member providing a support surface that is in frictional contact with each of the power adjusters, wherein the support member rotates about an axis that is centrally located within the support member, at least one platform for actuating axial movement of the support member and for actuating a shift in the axis of rotation of the power adjusters, wherein the platform provides a convex surface, at least one stationary support that is non-rotatable about the axis of rotation that is defined by the support member, wherein the at least one stationary support provides a concave surface, and a plurality of spindle supports, wherein each of the spindle supports are slidingly engaged with the convex surface of the platform and the concave surface of the stationary support, and wherein each of the spindle supports adjusts the axes of rotation of the power adjusters in response to the axial movement of the platform.
In another embodiment, the transmission comprises a rotatable driving member; three or more power adjusters, wherein each of the power adjusters respectively rotates about an axis of rotation that is respectively central to the power adjusters, a support member providing a support surface that is in frictional contact with each of the power adjusters, a rotatable driving member for rotating each of the power adjusters, a bearing disc having a plurality of inclined ramps for actuating the rotation of the driving member, a coiled spring for biasing the rotatable driving member against the power adjusters, at least one lock pawl ratchet, wherein the lock pawl ratchet is rigidly attached to the rotatable driving member, wherein the at least one lock pawl is operably attached to the coiled spring, and at least one lock pawl for locking the lock pawl ratchet in response to the rotatable driving member becoming disengaged from the power adjusters.
In still another embodiment, the transmission comprises a rotatable driving member, three or more power adjusters, wherein each of the power adjusters respectively rotates about an axis that is respectively central to each of the power adjusters, a support member providing a support surface that is in frictional contact with each of the power adjusters, wherein the support member rotates about an axis that is centrally located within the support member, a bearing disc having a plurality of inclined ramps for actuating the rotation of the driving member, a screw that is coaxially and rigidly attached to the rotatable driving member or the bearing disc, and a nut that, if the screw is attached to the rotatable driving member, is coaxially and rigidly attached to the bearing disc, or if the screw is rigidly attached to the bearing disc, coaxially and rigidly attached to the rotatable driving member, wherein the inclined ramps of the bearing disc have a higher lead than the screw.